Technically, the only guideline we're given is in the Size Rank Modifiers table on page 224 in the original Mutants and Mastermind Third Edition book. There is a similar table on page 274 in DCA, but with different numbers. The DCA Errata give the correct numbers which are also the ones in M&M3e p. 224.

There is no particular guide to the intermediate values, as they only cover the ranks that are divisible by 4. Presumably the other values are left to players and GMs to suss out.

However, I worked some out, and can actually be found on this page http://dicetales.net/rcu/dc_h/megaman_dca.htm. There's a table near the bottom of the page, and the first column is Height, the second is ranks of Growth, the third is ranks of Shrinking. Admittedly, it only goes to rank 16 in both directions. However, if you need to know 17, 18, or 19, go to 13, 14, and 15 and multiply the height by 2 (for Growth) or divide the height by 2 (for Shrinking)

It might be worth noting that Growth in M&M 3e doesn't just ignore the square cube law, it actually reverses it. Going from Growth 4 to Growth 8 doubles your height, and presumably multiplies your mass by eight... but it increases your strength by 4, which lets you lift sixteen times as much! When you use a universal table for all measurements, you get a few odd results out of it.

Last edited by RainOnTheSun on Mon Oct 09, 2017 11:48 pm, edited 1 time in total.

It might be worth noting that Growth in M&M 3e doesn't just ignore the square cube law, it actually reverses it. Going from Growth 4 to Growth 8 doubles your height, and presumably multiples your mass by eight... but it increases your strength by 4, which lets you lift sixteen times as much! When you use a universal table for all measurements, you get a few odd results out of it.